System and method for bare wafer inspection

ABSTRACT

A wafer inspection system includes a controller in communication with an electron-beam inspection tool. The controller includes circuitry to: acquire, via an optical imaging tool, coordinates of defects on a sample; set a Field of View (FoV) of the electron-beam inspection tool to a first size to locate a subset of the defects; determine a position of each defect of the subset of the defects based on inspection data generated by the electron-beam inspection tool during a scanning of the sample; adjust the coordinates of the defects based on the determined positions of the subset of the defects; and set the FoV of the electron-beam inspection tool to a second size to locate additional defects based on the adjusted coordinates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Application No. 16/517,390, filedJul. 19, 2019, which claims priority of US application 62/701,466 whichwas filed on Jul. 20, 2018, and both of which are is incorporated hereinby reference in their entireties its entireties.

TECHNICAL FIELD

The present disclosure generally relates to the field of semiconductorwafer metrology, and more particularly, to a system and method fordynamically inspecting a bare or un-patterned wafer using acharged-particle (e.g., electron) scanning tool.

BACKGROUND

In manufacturing processes of integrated circuits (ICs), unfinished orfinished circuit components need to be inspected to ensure that they aremanufactured according to design and are free of defects. Moreover,before being used to fabricate the ICs, a bare or un-patterned waferalso needs to be inspected to ensure it is free of defects or meets therequired specifications. As such, a bare-wafer inspection process hasbeen integrated into the manufacturing process.

Large defects on a bare wafer are visible with optical microscopy.However, as wafer processing conditions become increasingly stringent,the sizes of defects of interest are below the diffraction limit ofoptical microscopy. For example, as technology nodes are reduced down to10 nm, optical tools may generate a large amount of nuisance defects(i.e., false positives). In some optical inspection systems, 90% ofidentified defects may turn out to be nuisance defects. Therefore, it isimportant to review the identified defects and confirm whether they arereal defects.

SUMMARY

Embodiments of the present disclosure relate to systems and methods forinspecting a bare wafer. In some embodiments, a defect review tool isprovided. The tool includes a controller in communication with anelectron-beam inspection tool. The controller includes circuitry to:acquire, via an optical imaging tool, coordinates of defects on asample; set a Field of View (FoV) of the electron-beam inspection toolto a first size to locate a subset of the defects; determine a positionof each defect of the subset of the defects based on inspection datagenerated by the electron-beam inspection tool during a scanning of thesample; adjust the coordinates of the defects based on the determinedpositions of the subset of the defects; and set the FoV of theelectron-beam inspection tool to a second size to locate additionaldefects based on the adjusted coordinates.

In some embodiments, a wafer inspection system is provided. The systemincludes an optical imaging tool configured to illuminate a sample witha laser beam and detect light scattered from the sample. The system alsoincludes an electron-beam inspection tool configured to scan the samplewith a primary electron beam to generate inspection data. The systemfurther includes a controller in communication with the optical imagingtool and the electron-beam inspection tool. The controller includescircuitry to: receive light-scattering data generated by the opticalimaging tool; determine coordinates of defects on the sample based onthe light-scattering data; set a Field of View (FoV) of theelectron-beam inspection tool to a first size to locate a subset of thedefects; determine a position of each defect of the subset of thedefects based on inspection data generated by the electron-beaminspection tool during a scanning of the sample; adjust the coordinatesof the defects based on the determined positions of the subset of thedefects; and set the FoV of the electron-beam inspection tool to asecond size to locate additional defects based on the adjustedcoordinates.

In some embodiments, a controller is provided. The controller is coupledwith an electron-beam inspection tool which scans a sample with aprimary electron beam to generate inspection data. The controllerincludes a memory storing instructions. The controller also includes aprocessor configured to execute the instructions to cause the controllerto: acquire, via an optical imaging tool, coordinates of defects on thesample; set a Field of View (FoV) of the electron-beam inspection toolto a first size to locate a subset of the defects; determine a positionof each defect of the subset of the defects based on inspection datagenerated by the electron-beam inspection tool during a scanning of thesample; adjust the coordinates of the defects based on the determinedpositions of the subset of the defects; and set the FoV of theelectron-beam inspection tool to a second size to locate additionaldefects based on the adjusted coordinates.

In some embodiments, a computer-implemented wafer inspection method isprovided. The method includes acquiring, via an optical imaging tool,coordinates of defects on a sample. The method also includes setting aField of View (FoV) of an electron-beam inspection tool to a first sizeto locate a subset of the defects. The method also includes determininga position of each defect of the subset of the defects based oninspection data generated by the electron-beam inspection tool during ascanning of the sample. The method also includes adjusting thecoordinates of the defects based on the determined positions of thesubset of the defects. The method further includes setting the FoV ofthe electron-beam inspection tool to a second size to locate additionaldefects based on the adjusted coordinates.

In some embodiments, a non-transitory computer-readable medium isprovided. The medium stores a set of instructions that are executable bya processor of a devices to cause the device to perform a methodincluding: acquiring, via an optical imaging tool, coordinates ofdefects on a sample; setting a Field of View (FoV) of an electron-beaminspection tool to a first size to locate a subset of the defects;determining a position of each of the subset of the defects based oninspection data generated by the electron-beam inspection tool during ascanning of the sample; adjusting the coordinates of the defects basedon the determined positions of the subset of the defects; and settingthe FoV of the electron-beam inspection tool to a second size to locateadditional defects based on the adjusted coordinates.

Additional objects and advantages of the disclosed embodiments will beset forth in part in the following description, and in part will beapparent from the description, or may be learned by practice of theembodiments. The objects and advantages of the disclosed embodiments maybe realized and attained by the elements and combinations set forth inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosed embodiments, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an exemplary electron-beaminspection tool for inspecting a wafer, consistent with embodiments ofthe present disclosure.

FIG. 2 is a schematic diagram illustrating an exemplary optical imagingtool for inspecting a wafer, consistent with embodiments of the presentdisclosure.

FIG. 3 is a block diagram of a defect inspection tool for inspecting abare wafer, consistent with embodiments of the present disclosure.

FIG. 4 is a flowchart of a method for bare wafer inspection, consistentwith embodiments of the present disclosure.

FIG. 5 is a schematic diagram illustrating an implementation of themethod of FIG. 4 , consistent with embodiments of the presentdisclosure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings. The followingdescription refers to the accompanying drawings in which the samenumbers in different drawings represent the same or similar elementsunless otherwise represented. The implementations set forth in thefollowing description of exemplary embodiments do not represent allimplementations consistent with the invention. Instead, they are merelyexamples of apparatuses and methods consistent with aspects related tothe invention as recited in the appended claims

Before being used for IC fabrication, a bare wafer (or “un-patterned”wafer, “blank” wafer) needs to be inspected to ensure it is free ofdefects. For example, the bare wafer needs to be inspected forcontamination (e.g., particles, metal contaminants) and surface quality(e.g., pits, scratches, crystal defects), which may adversely affect thewafer yield (i.e., how many good-quality circuit units can be made froma wafer) or performance of the manufactured circuits (e.g., shortcircuit, bad contact, etc., that can impair the proper functioning of acircuit). Moreover, the result of the bare-wafer inspection is a goodindication of the cleanliness of the fabrication or metrology equipment.If the bare wafer has a high defect density, the fabrication ormetrology equipment needs to be cleaned before the fabrication processis started.

Currently, bare-wafer inspection is often performed by opticalmicroscopy. However, as described above, as the semiconductor industryis striving to make smaller circuits, the size of the defects that canimpact the circuit manufacturing and functioning, and thus need to bedetected, is also becoming smaller (e.g., down to the order of 10 nm,which is below the typical optical wavelength). Therefore, theinspection result reported by the optical microscopy may contain a largenumber of inaccuracies, e.g., false positives.

Charged-particle (e.g., electron) beam microscopes, such as a scanningelectron microscope (SEM), may be used to review the defects identifiedby an optical microscope, because when compared to a photon beam, anelectron beam has a shorter wavelength and thereby may offer superiorspatial resolution. In practice, a bare wafer may be first placed underan optical microscope to identify potential defect locations. The barewafer is then transferred to a SEM, and the potential defect locationsmay be further examined by the SEM to determine whether they correspondto real defects. Therefore, it is needed for the optical microscope tocommunicate the locations of the potential defects to the SEM, or forthe SEM to “know” the locations of the potential defects as identifiedby the optical microscope.

Because the bare wafer is devoid of patterns, the locations of defectscannot be indicated by referring to the wafer itself but rather have tobe expressed in terms of mathematical coordinates on the imagesgenerated by the optical microscope and the SEM. However, because thealignments of the wafer on the optical microscope and the SEM are notidentical, the same defect may have different coordinates on the opticalimage and the SEM image (hereinafter referred to as “optical mapcoordinates” and “electron map coordinates,” respectively). That is, inthe SEM's field of view (FoV), the defect may not be exactly at itsoptical map coordinates. Therefore, to locate the defect, the SEM has tosearch in the vicinity of the defect's optical map coordinates until thedefect is found. This is time consuming, particularly because thescanning speed of the SEM is low.

The present disclosure provides a system and method for improving thethroughput for inspecting a bare wafer. The bare wafer can be firstimaged by an optical imaging tool to identify potential defects, andthen scanned by a SEM to verify whether the potential defects are realdefects. The SEM performs the bare-wafer inspection in two phases—(1) acalibration phase and (2) a review phase. In the calibration phase, theSEM calibrates the difference between the defects' optical mapcoordinates and electron map coordinates. Specifically, a subset of thepotential defects is selected. For each of the selected potentialdefects, the SEM searches in a vicinity of the location corresponding tothe defect's optical map coordinates, using a FoV that is large enoughto cover the wafer alignment error. This way, if the locationcorresponding to a potential defect's optical map coordinates falls inthe SEM's field of view, the potential defect itself also falls in theSEM's field of view, such that the SEM can find the potential defect anddetermine the defect's electron map coordinates by just scanning thecurrent field of view (i.e., in a single image). After the SEM locatesall selected potential defects and determines their electron mapcoordinates, a transformation relationship (e.g., a transformationmatrix) between the optical imaging tool's coordinate system and theSEM's coordinate system is determined based on the selected potentialdefects' optical map coordinates and electron map coordinates.

After the transformation relationship is determined, the SEM locates andreviews the remaining potential defects in the review phase, using asmaller FoV. Specifically, the remaining potential defects' electron mapcoordinates may be determined based on their optical map coordinates andthe transformation relationship. The SEM then searches for the remainingpotential defects in vicinities surrounding their determined electronmap coordinates. The errors between the determined electron mapcoordinates and the remaining potential defects' true locations in theSEM's field of view are usually small enough to be covered by thesmaller FoV. This way, despite the reduced FoV size, as long as thelocation corresponding to a potential defect's determined electron mapcoordinates falls in the SEM's field of view, the SEM can find thepotential defect by just scanning the current field of view (i.e., in asingle image).

As described above, the disclosed method controls the SEM to use a largeFoV in the calibration phase, while using a small FoV in the reviewphase. In the calibration phase, the large FoV enables the SEM to locatea potential defect in a current field of view, without the need ofsearching in multiple images. Therefore, despite the transformationrelationship between the optical map coordinates and electron mapcoordinates being unknown, the amount of time used in searching for thepotential defects can be reduced. In the review phase, using thetransformation relationship developed during the calibration phase, ittakes less time to scan for the identified defects using the small FoV,thereby further speeding up the defect-locating process. It can be seenthat by dynamically switching the SEM from the large FoV to the smallFoV, the disclosed method enables the SEM to quickly and accuratelylocate potential defects. Accordingly, the system throughput forinspecting the bare wafer is drastically improved.

As used throughout this disclosure, unless specifically statedotherwise, the term “or” encompasses all possible combinations, exceptwhere infeasible. For example, if it is stated that a device can includeA or B, then, unless specifically stated otherwise or infeasible, thedevice can include A, or B, or A and B. As a second example, if it isstated that a device can include A, B, or C, then, unless specificallystated otherwise or infeasible, the device can include A, or B, or C, orA and B, or A and C, or B and C, or A and B and C.

FIG. 1 is a schematic diagram illustrating an exemplary electron beam(e-beam) tool 100, consistent with the disclosed embodiments. As shownin FIG. 1 , a primary electron beam 125 is emitted from a cathode 101 byapplying a voltage between an anode 102 and cathode 101. Primaryelectron beam 125 passes through a gun aperture 103 and a beam limitaperture 104, both of which can determine the current of electron beamentering a condenser lens 105, which resides below beam limit aperture104. Condenser lens 105 focuses primary electron beam 125 before thebeam enters an objective aperture 108 to set the current of the electronbeam before entering a compound objective lens 116. In some embodiments,e-beam tool 100 may also include an astigmatism corrector 106 or a beamblanker module 107, for adjusting the beam profile of primary electronbeam 125.

Compound objective lens 116 is configured to form a magnetic field andan electrostatic field for focusing primary electron beam 125 onto awafer 120 and forming a probe spot 123 on a surface of wafer 120.Compound objective lens 116 may include an upper pole piece 116 a, ashared pole piece 116 b, and a lower pole piece 116 c. Upper pole piece116 a and shared pole piece 116 b constitute a conical magnetic lens,which has an excitation coil 116 d. Shared pole piece 116 b and lowerpole piece 116 c constitute an immersion magnetic lens, which has anexcitation coil 116 e. The conical magnetic lens and the immersionmagnetic lens share the same shared pole piece 116 b.

When electric currents are applied onto excitation coils 116 d and 116e, respectively, an axially-symmetric magnetic field is generated ontothe wafer surface area. A part of wafer 120 being scanned by primaryelectron beam 125 can be immersed in the magnetic field. Differentvoltages are applied onto wafer 120, upper pole piece 116 a, and sharedpole piece 116 b, to generate an axial symmetric retarding electricfield near the wafer surface. The electric field reduces the energy ofimpinging primary electron beam 125 near the surface of the wafer beforeit collides with wafer 120. Shared pole piece 116 b controls anaxially-symmetric electric field on the wafer to prevent micro-arcing ofthe wafer and to ensure proper beam focus at the wafer surface with theaxially-symmetric magnetic field together.

E-beam tool 100 also includes an X-Y stage 126 a and a Z stage 126 b formoving wafer 120 to the axial area of primary electron beam 125 andadjusting the height of wafer 120 to the focused-imaging plane ofprimary electron beam 125.

A pre-lens deflector 110 (e.g., a deflector upstream of the compoundobjective lens) and an in-lens deflector 112 (e.g., a deflector in thecompound objective lens) deflect primary electron beam 125 to scan probespot 123 over wafer 120. For example, in a scanning process, deflectors110, 112 can be controlled to deflect primary electron beam 125sequentially onto different locations of top surface of wafer 120 atdifferent time points, to provide data for image reconstruction fordifferent parts of wafer 120. Moreover, deflectors 110, 112 can also becontrolled to deflect primary electron beam 125 onto different sides ofwafer 120 at a particular location, at different time points, to providedata for stereo image reconstruction of the wafer structure at thatlocation. Further, in some embodiments, anode 102 and cathode 101 can beconfigured to generate multiple primary electron beams 125, and e-beamtool 100 can include multiple sets of deflectors 110, 112 to project themultiple primary electron beams 125 to different parts/sides of wafer120 at the same time.

A secondary electron beam 111 can be emitted from the part of wafer 120upon receiving primary electron beam 125. A cross-electromagnetic (E×B)alignment unit 114 aligns the optical axis of secondary electron beam111 with the optical axis of primary electron beam 125. Secondaryelectron beam 111 can be received by sensor surfaces 109 a and 109 b ofan electron detector 109. Electron detector 109 can generate a signal(e.g., a voltage, a current, etc.) that represents an intensity ofsecondary electron beam 111, and provide the signal to a processingsystem (not shown in FIG. 1 ). The intensity of secondary electron beam111 can vary according to the external or internal structure of wafer120. Moreover, as discussed above, primary electron beam 125 can beprojected onto different locations of the top surface of wafer 120, ordifferent sides of wafer 120 at a particular location, to generatesecondary electron beams 111 of different intensities. Therefore, bymapping the intensity of secondary electron beam 111 with the locationsof wafer 120, the processing system can reconstruct an image thatreflects the internal or external structures of wafer 120.

Consistent with the disclosed embodiments, a FoV and resolution ofe-beam tool 100 can be adjusted by changing the structural configurationor controlling the operation of compound objective lens 116.Specifically, the magnetic field and the electrostatic field formed bycompound objective lens 116 can be controlled to change the landingenergy of primary electron beam 125 or the size of scan probe spot 123.

For example, the distance from the bottom surface of shared pole piece116 b to the wafer surface 120 can be a distance within the range from1.0 to 8.0 mm. The bore size of shared pole piece 116 b can be adimension within the range from 1.0 to 30.0 mm. These two dimensions canbe used to provide the appropriate electrostatic and magnetic fieldstrength at the wafer surface and an appropriate probe size. To achievea large FoV (and thus a relatively low resolution), a relatively longdistance between shared pole piece 116 b to the wafer surface 120 andlarger bore size are preferred. Under this configuration, the conicalmagnetic lens, formed by upper pole piece 116 a and shared pole piece116 b, works as the primary focusing objective lens. Therefore, highlanding energy beam and a large scanning FoV (and low resolution) areachievable. In contrast, to achieve a small FoV (and thus a relativelyhigh resolution), a shorter distance between the shared pole piece 116 bto the wafer surface 120 and small bore size are used. Under thisconfiguration, the immersion magnetic lens, formed by shared pole piece116 b and lower pole piece 116 c, works as the primary focusingobjective lens. Therefore, a low landing energy beam and a smallscanning FoV (and high resolution) are achievable.

Additionally or alternatively, the landing energy of primary electronbeam 125 or the size of scan probe spot 123 can also be adjusted bycontrolling the strength of the conical magnetic lens or the immersionmagnetic lens. As described above, different voltages may be appliedonto wafer 120, upper pole piece 116 a, and shared pole piece 116 b, toadjust the strength of the electric field near wafer 120. When theelectric field generated by the conical magnetic lens (i.e., upper polepiece 116 a and shared pole piece 116 b) is stronger, the conicalmagnetic lens works as the primary focusing objective lens, therebyachieving the large scanning FoV and low resolution. When the electricfield generated by the immersion magnetic lens (i.e., shared pole piece116 b and wafer 120) is stronger, the immersion magnetic lens works asthe primary focusing objective lens, thereby achieving the smallerscanning FoV and higher resolution. In the disclosed embodiments, inorder to apply various voltages onto shared pole piece 116 b, sharedpole piece 116 b is electrically insulated from upper pole piece 116 a.

Although FIG. 1 shows e-beam tool 100 as a single-beam inspection tool,it is contemplated that e-beam tool 100 may also be a multi-beaminspection tool that uses multiple primary electron beams. As describeabove, e-beam tool 100 may be configured to generate multiple primaryelectron beams 125 for simultaneously probing multiple areas of wafer120. Correspondingly, e-beam tool 100 may also include multiples sets ofcompound objective lens 116 (i.e., multiple sets of conical magneticlens and immersion magnetic lens) for focusing the multiple primaryelectron beams 125, respectively. The multiple sets of compoundobjective lens 116 may be controlled collectively or individually toadjust FoV sizes of the multiple primary electron beams 125 collectivelyor individually. As it will be evident from the following description,the principles disclosed in the present disclosure can be applied inboth single-beam and multi-beam inspection tools.

Consistent with the disclosed embodiments, e-beam tool 100 also includesa controller 140 that includes a memory 142, an image acquirer 144, anda processor 146. Processor 146 may include a computer, server, mainframehost, terminals, personal computer, any kind of mobile computingdevices, a microprocessor-based system, a microcontroller, an embeddedsystem (e.g., firmware), or any other suitable control circuit orsystem. Processor 146 may be specially configured with hardware orsoftware modules for controlling the operation of e-beam tool 100. Forexample, processor 146 may change the voltage applied to shared polepiece 116 b, so as to adjust the FoV size of e-beam tool 100.

Image acquirer 144 may be a computer system similar to processor 146.Image acquirer 144 may connect with detector 109 through a medium suchas an electrical conductor, optical fiber cable, portable storage media,IR, Bluetooth, internet, wireless network, wireless radio, or acombination thereof. Image acquirer 144 may receive a signal fromdetector 109 and may construct an image of wafer 120. Image acquirer 144may also perform various post-processing functions, such as generatingcontours, superimposing indicators on an acquired image, and the like.Image acquirer 144 may be configured to perform adjustments ofbrightness and contrast, etc. of acquired images.

Memory 142 may be a storage medium such as a random access memory (RAM),a hard disk, cloud storage, other types of computer readable memory, andthe like. Memory 142 may be coupled with image acquirer 144 andprocessor 146. Memory 142 stores computer instructions or programs thatare accessible and executable by image acquirer 144 and processor 146for performing functions consistent with the present disclosure. Memory142 may also be used for saving scanned raw image data as originalimages and post-processed images.

As described above, optical microscopy can be used to detect potentialdefect locations on a bare wafer. FIG. 2 is a schematic diagramillustrating an exemplary optical imaging tool 200 for inspecting awafer, consistent with embodiments of the present disclosure. Referringto FIG. 2 , optical imaging tool 200 includes a laser 210 for projectingan incident laser beam 211 to a wafer 120. The laser light will bescattered by wafer 120 and the scattered light 221 is detected by alight detector 220. When incident laser beam 211 hits a defect 121 onwafer 120, the intensity of scattered light 221 will change. Thus, byanalyzing the intensity change of scattered light 221, potential defectscan be detected.

Optical imaging tool 200 may also include a sample stage (not shown)configured to rotate wafer 120 along the tangential direction 232 andmove wafer 120 in the radial direction 234. This way, incident laserbeam 211 can irradiate the entire surface of wafer 120 to detect thepotential defects. Based on the wafer rotation angle and the radiusposition of the laser beam, the position coordinates of theparticle/defect are calculated and registered.

FIG. 3 is a schematic diagram illustrating an exemplary electron-beaminspection (EBI) system 30 for detecting detects on a bare wafer,consistent with embodiments of the present disclosure. As shown in FIG.3 , EBI system 30 includes a main chamber 31, a load/lock chamber 32, anoptical imaging tool 200, an e-beam tool 100, and an equipment front endmodule (EFEM) 36. Optical imaging tool 200 and e-beam tool 100 arelocated within main chamber 31 and are connected by asample-transferring chamber 34.

EFEM 36 includes a first loading port 36 a and a second loading port 36b. EFEM 36 may include additional loading port(s). First loading port 36a and second loading port 36 b can receive wafer front opening unifiedpods (FOUPs) that contain bare wafers (e.g., semiconductor wafers orwafers made of other material(s)). One or more robot arms (not shown) inEFEM 36 may transport the bare wafers to load/lock chamber 32. Forexample, the robot arms may include an actuator for driving a belt totransport the bare wafers to load/lock chamber 32. The robot arms mayalso include circuitry configured to send control signals to theactuator.

Load/lock chamber 32 is connected to a load/lock vacuum pump system (notshown), which removes gas molecules in load/lock chamber 32 to reach afirst pressure below the atmospheric pressure. After reaching the firstpressure, one or more robot arms (not shown) may transport the barewafer from load/lock chamber 32 to main chamber 31. Main chamber 31 isconnected to a main chamber vacuum pump system (not shown), whichremoves gas molecules in main chamber 31 to reach a second pressurebelow the first pressure. After reaching the second pressure, the barewafer is subject to inspection by optical imaging tool 200 to detectpotential defect locations. After optical imaging tool 200 finishesscanning the bare wafer, one or more robot arms (not shown) insample-transferring chamber 34 may transport the bare wafer to e-beamtool 100 for verifying whether the potential defects are real defects.E-beam tool 100 may be a single-beam tool or a multi-beam tool.

EBI system 30 may also include a computer system, e.g., controller 38,configured to execute various controls of EBI system 30. Consistent withthe disclosed embodiments, controller 38 may be electronically connectedto e-beam tool 100 or optical imaging tool 200. For example, controller38 may include circuitry and memory (e.g., such as the circuitry andmemory of controller 140 of FIG. 1 ) configured to control e-beam tool100 or optical imaging tool 200 to scan a bare wafer, receive image datafrom e-beam tool 100 or optical imaging tool 200, and analyze the imagedata to inspect defects on the bare wafer. As another example,controller 38 may also include circuitry configured to control e-beamtool 100 to switch between different FoV sizes while scanning the barewafer. While controller 38 is shown in as being outside of the structurethat include main chamber 31, load/lock chamber 32, and EFEM 36, it isappreciated that controller 38 can be integrated inside the structure.

FIG. 4 is a flowchart of a method 40 for bare wafer inspection,consistent with embodiments of the present disclosure. For example,method 40 may be performed by EBI system 30. Referring to FIG. 4 ,method 40 may include the following steps 402-416.

In step 402, a bare wafer (e.g., wafer 120) is loaded to an e-beam tool(e.g., e-beam tool 100). In some embodiments, before being inspected bythe e-beam tool, the bare wafer is first inspected by an optical imagingtool (e.g., optical imaging tool 200) to detect potential defectlocations. As described above, because of the low resolution of theoptical imaging tool, the potential defects may include false positivesand may need to be examined by the e-beam tool. Thus, after beinginspected by the optical imaging tool, the bare wafer is transferred toand loaded on a sample stage (e.g., stage 126) of the e-beam tool.

In step 404, the e-beam tool aligns the bare wafer according to a notchon the bare wafer. As described above, the bare wafer has no printedpatterns that can serve as reference marks for determine itsorientation. In some embodiments, the bare wafer's edge may be providedwith a notch (e.g., notch 122 in FIG. 5 ) to mark its direction. Boththe optical imaging tool and e-beam tool may align the bare wafer basedon the notch. This way, the wafer alignment error can be limited.

In step 406, the e-beam tool (e.g., controller 140) selects at least twopotential defects identified by the optical image tool. Consistent withthe disclosed embodiments, the e-beam tool may randomly select the atleast two potential defects and obtain their optical map coordinates(i.e., coordinates in the optical imaging tool's coordinate system).

In step 408, the e-beam tool locates the selected potential defects byspiral searching the selected defects with a large scanning FoV. In thedisclosed embodiments, although the wafer may be aligned on the opticalimaging tool and e-beam tool based on the wafer notch, this is onlyrough alignment and there may be large errors. Moreover, the samplestages and mounting structures used in the optical imaging tool ande-beam tool are not identical. Therefore, the optical imaging tool ande-beam tool may have different coordinate systems (i.e., the same defecton the bare wafer has different optical map coordinates and electron mapcoordinates). Thus, a transformation relationship between these twocoordinate systems needs to be calibrated. In addition, thistransformation relationship will change every time when the bare waferis remounted on the optical imaging tool or e-beam tool, or when adifferent bare wafer is inspected. Therefore, the calibration may beconstantly performed.

Because a potential defect's optical map coordinates do not indicate itstrue location in the e-beam tool's field of view, the e-beam tool maysearch the potential defect in a vicinity of the optical mapcoordinates, until the potential defect is found. As described inconnection with FIG. 1 , the e-beam tool may operate in large and smallFoVs. To locate the selected potential defects, the e-beam tool may beswitched to a FoV that is large enough to cover the wafer alignmenterrors, but with a pixel size that is sensitive to detecting thedefects. By controlling the sample stage to move the bare wafer in itsradial and tangential directions, the e-beam tool may perform a spiralsearching of the selected potential defects using the large FoV. In someembodiments, search patterns other than spiral searching are utilized tosearch for the selected potential defects. The search patterns can beany search pattern that may enable the selected potential defects to belocated.

Referring back to FIG. 4 , in step 410, after locating the selectedpotential defects, the e-beam tool determines the selected potentialdefects' electron map coordinates in the e-beam tool's field of view.Based on the selected potential defects' optical map coordinates andelectron map coordinates, a transformation matrix may be determined.

In step 412, the e-beam tool locates additional potential defects basedon the transformation matrix. Specifically, the transformation matrix isapplied to the additional potential defects' optical map coordinates toobtain transformed coordinates. After that, the e-beam tool may searchfor the additional potential defects in vicinities of the transformedcoordinates, using the large FoV.

In step 414, the accuracy of the transformed defect coordinates arechecked. Consistent with the disclosed embodiments, if thetransformation matrix is accurate, the transformed coordinates should beclose to the additional potential defects' true positions in the e-beamtool's field of view (e.g., the additional potential defects' electronmap coordinates). In some embodiments, differences (e.g., distances)between the transformed coordinates and the corresponding defects' truepositions are compared. If the differences exceed a predeterminedthreshold, this indicates that the transformation matrix is not accurateand may need to be updated. Thus, method 40 may return to step 410, atwhich the transformation matrix is updated based on the additionalpotential defects' optical map coordinates and electron map coordinates.Consistent with the disclosed embodiments, steps 410-414 may bereiterated until the transformation matrix is determined to be accurate.

In step 416, after the transformation matrix is determined to beaccurate, the e-beam tool may switch to a small FoV and locate theremaining potential defects based on their transformed coordinates.Specifically, the transformation matrix may be applied to the remainingpotentials defects' optical map coordinates to obtain transformedcoordinates. The e-beam tool then searches for the remaining potentialdefects in vicinities of their transformed coordinates, using the smallFoV. Because the transformation matrix is accurate, the error betweenthe transformed coordinates and the corresponding defects' true electronmap coordinates is small and can be covered by the small FoV. Moreover,because the small FoV has a high resolution, the e-beam tool canaccurately determine whether the potential defects are real defects.

By dynamically switching the e-beam tool from the large FoV to the smallFoV, the system throughput for inspecting the bare wafer is improved.FIG. 5 is a schematic diagram illustrating an implementation of themethod 40, consistent with some embodiments of the present disclosure.As shown in FIG. 5 , in calibration phase 51, the wafer alignment erroris calibrated based on differences between the optical map coordinatesand electron map coordinates of a set of selected potential defects.Specifically, the e-beam tool first performs a spiral searching of theselected potential defects on the bare wafer, using a large FoV. Thee-beam tool may generate multiple images during the spiral searching.Since the large FoV is enough to cover the wafer alignment error, aselected potential defect and the position corresponding to the defect'soptical map coordinates may be covered by the same image. Therefore, thee-beam tool can locate a selected potential defect by just examining asingle image that includes the position corresponding to defect'soptical map coordinates, thereby avoiding the need of searching for thedefect across multiple images. This way, the selected potential defectscan be quickly located and used to determine a transformationrelationship between the optical imaging tool's coordinate system andthe e-beam tool's coordinate system.

After the calibration is completed, the e-beam tool may inspect theremaining potential defects on the bare wafer in review phase 52, usinga small FoV. Specifically, the calibrated transformation relationshipmay be used to estimate the remaining potential defects' electron mapcoordinates based on their optical map coordinates. The SEM may searchfor the remaining potential defects in vicinities of their estimatedcoordinates. The small FoV is enough to cover the errors between theestimated coordinates and the remaining potential defects' truepositions. Because it takes less time to scan a small FoV, the speed forlocating and inspecting the remaining potential defects is increased.Accordingly, by dynamically switching the e-beam tool from the large FoVto the small FoV for the calibration phase and review phase,respectively, the system throughput is improved.

Consistent with the disclosed embodiments, in both the large and smallFoVs, the resolution of the e-beam tool and the uniformity of its imagefocus are configured to be high enough for detecting the defects. Thisway, the disclosed method can quickly and accurately inspecting defectson a bare wafer.

It is appreciated that a controller of EBI system 30 could use softwareto control some functionality described above. For example, thecontroller could generate instructions for controlling the e-beam toolto switch between the large and small FoVs. As another example, thecontroller may receive image data from the e-beam tool 100 to opticalimaging tool 200, and identify and locate defects from the images. Forexample another example, controller may compute the transformationmatrix for the coordinate systems of the e-beam tool and optical imagingtool. The software could be stored on a non-transitory computer readablemedium. Common forms of non-transitory media include, for example, afloppy disk, a flexible disk, hard disk, solid state drive, magnetictape, or any other magnetic data storage medium, a CD-ROM, any otheroptical data storage medium, any physical medium with patterns of holes,a RAM, a PROM, and EPROM, a FLASH-EPROM or any other flash memory,NVRAM, a cache, a register, any other memory chip or cartridge, andnetworked versions of the same.

The embodiments may further be described using the following clauses:

-   -   1. A defect review tool comprising:        -   a controller in communication with an electron-beam            inspection tool, the controller having circuitry to:            -   acquire, via an optical imaging tool, coordinates of                defects on a sample;            -   set a Field of View (FoV) of the electron-beam                inspection tool to a first size to locate a subset of                the defects;            -   determine a position of each defect of the subset of the                defects based on inspection data generated by the                electron-beam inspection tool during a scan of the                sample;            -   adjust the coordinates of the defects based on the                determined positions of the subset of the defects; and            -   set the FoV of the electron-beam inspection tool to a                second size to locate additional defects based on the                adjusted coordinates.    -   2. The defect review tool of clause 1, wherein the first size is        larger than the second size.    -   3. The defect review tool of any one of clauses 1 and 2, wherein        the sample is an un-patterned wafer.    -   4. The defect review tool of any one of clauses 1-3, wherein the        controller having circuitry to adjust the coordinates of the        defects based on the determined positions of the subset of the        defects includes the controller having circuitry to:        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            subset of the defects;        -   map the coordinates acquired via the optical imaging tool to            a new set of coordinates, based on the transformation            relationship; and        -   set the new set of coordinates as the adjusted coordinates.    -   5. The defect review tool of any one of clauses 1-3, wherein the        controller having circuitry to adjust the coordinates of the        defects based on the determined positions of the subset of the        defects includes the controller having circuitry to:        -   select a number of defects;        -   control the electron-beam inspection tool to locate the            selected detects;        -   determine positions of the selected defects based on the            inspection data;        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            selected defects; and        -   adjust the coordinates of the defects based on the            transformation relationship.    -   6. The defect review tool of clause 5, wherein the controller        has circuitry to select at least two defects as the subset of        the defects.    -   7. The defect review tool of clause 5, wherein the controller        having circuitry to set the FoV of the electron-beam inspection        tool to the second size includes the controller having circuitry        to:        -   control the electron-beam inspection tool to locate a first            defect, the first defect being different from the selected            defects;        -   determine a position of the first defect based on the            inspection data;        -   determine a difference between the determined position of            the first defect and an adjusted coordinate of the first            defect; and        -   when the difference is equal to or below a predetermined            threshold, change the FoV of the electron-beam inspection            tool to the second size to locate additional defects based            on the adjusted coordinates.    -   8. The defect review tool of clause 7, wherein the controller        has circuitry to:        -   when the difference exceeds the predetermined threshold,            update the transformation relationship based on the            determined position of the first defect; and        -   further adjust the coordinates of the defects based on the            updated transformation relationship.    -   9. The defect review tool of any one of clauses 1-8, wherein the        optical imaging tool is a laser-scattering defect inspection        tool having circuitry to illuminate the sample with a laser beam        and to detect light scattered from the sample.    -   10. The defect review tool of clause 9, wherein the controller        has circuitry to:        -   receive light-scattering data from the optical imaging tool;            and        -   determine the coordinates of the defects based on the            light-scattering data.    -   11. The defect review tool of any one of clauses 1-10, wherein        the electron-inspection tool comprises:        -   an electron source configured to generate a primary electron            beam;        -   at least one condenser lens for condensing the primary            electron beam;        -   a compound objective lens for focusing the primary electron            beam to the sample on a stage system, the compound objective            lens comprising:            -   a first magnetic lens;            -   a second magnetic lens, wherein a shared pole piece is                configured for both the first magnetic lens and the                second magnetic lens; and        -   an electrostatic lens; and        -   a detection system for detecting charged particles or X-ray            emanated from the sample.    -   12. The defect review tool of clause 11, wherein the first        magnetic lens comprises an upper pole piece and a first        excitation coil.    -   13. The defect review tool of clause 12, wherein the second        magnetic lens comprises a lower pole piece and a second        excitation coil.    -   14. The defect review tool of clause 13, wherein the shared pole        piece is isolated from the upper pole piece.    -   15. The defect review tool of clause 14, wherein the shared pole        piece is isolated from the lower pole piece.    -   16. The defect review tool of clause 15, wherein the        electrostatic lens comprises the upper pole piece, the shared        pole piece, and the sample.    -   17. The defect review tool of clause 16, wherein the first        magnetic lens is conical.    -   18. The defect review tool of clause 17, wherein the second        magnetic lens is an immersion lens.    -   19. The defect review tool of clause 13, wherein the lower pole        piece is isolated from the second magnetic lens.    -   20. The defect review tool of clause 15, wherein the lower pole        piece is isolated from the second magnetic lens.    -   21. The defect review tool of clause 11, wherein the shared pole        piece is electrically isolated from the first magnetic lens and        the second magnetic lens.    -   22. A system comprising:        -   an optical imaging tool including circuitry to illuminate a            sample with a laser beam and detect light scattered from the            sample;        -   an electron-beam inspection tool including circuitry to scan            the sample with a primary electron beam to generate            inspection data; and        -   a controller in communication with the optical imaging tool            and the electron-beam inspection tool, the controller            including circuitry to:            -   receive light-scattering data generated by the optical                imaging tool;            -   determine coordinates of defects on the sample based on                the light-scattering data;            -   set a Field of View (FoV) of the electron-beam                inspection tool to a first size to locate a subset of                the defects;            -   determine a position of each defect of the subset of the                defects based on inspection data generated by the                electron-beam inspection tool during a scan of the                sample;            -   adjust the coordinates of the defects based on the                determined positions of the subset of the defects; and            -   set the FoV of the electron-beam inspection tool to a                second size to locate additional defects based on the                adjusted coordinates.    -   23. The system of clause 22, wherein the electron-beam        inspection tool including circuitry to scan the sample with the        primary electron beam includes the electron-beam inspection tool        including circuitry to scan the sample with multiple electron        beams.    -   24. The system of any one of clauses 22 and 23, further        comprising:        -   a transport device including circuitry and an actuator to            transport the sample from the optical imaging tool to the            electron-beam inspection tool.    -   25. The system of any one of clauses 22-24, wherein the first        size is larger than the second size.    -   26. The system of any one of clauses 22-25, wherein the sample        is an un-patterned wafer.    -   27. The defect review tool of any one of clauses 22-26, wherein        the controller including circuitry to adjust the coordinates of        the defects based on the determined positions of the subset of        the defects includes the controller including circuitry to:        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            subset of the defects;        -   map the coordinates acquired via the optical imaging tool to            a new set of coordinates, based on the transformation            relationship; and        -   set the new set of coordinates as the adjusted coordinates.    -   28. The system of any one of clauses 22-26, wherein the        controller including circuitry to adjust the coordinates of the        defects based on the determined positions of the subset of the        defects includes the controller including circuitry to:        -   select a number of defects;        -   control the electron-beam inspection tool to locate the            selected detects;        -   determine positions of the selected defects based on the            inspection data;        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            selected defects; and        -   adjust the coordinates of the defects based on the            transformation relationship.    -   29. The system of clause 28, wherein the controller has        circuitry to select at least two defects as the subset of the        defects.    -   30. The system of clause 28, wherein the controller including        circuitry to set the FoV of the electron-beam inspection tool to        a second size includes the controller including circuitry to:        -   control the electron-beam inspection tool to locate a first            defect, the first defect being different from the selected            defects;        -   determine a position of the first defect based on the            inspection data;        -   determine a difference between the determined position of            the first defect and an adjusted coordinate of the first            defect; and        -   when the difference is equal to or below a predetermined            threshold, change the FoV of the electron-beam inspection            tool to the second size to locate additional defects based            on the adjusted coordinates.    -   31. The system of clause 30, wherein the controller includes        circuitry to:        -   when the difference exceeds the predetermined threshold,            update the transformation relationship based on the            determined position of the first defect; and        -   further adjust the coordinates of the defects based on the            updated transformation relationship.    -   32. A controller coupled with an electron-beam inspection tool        configured to scan a sample with a primary electron beam to        generate inspection data, the controller comprising:        -   a memory storing instructions; and        -   a processor configured to execute the instructions to cause            the controller to:            -   acquire, via an optical imaging tool, coordinates of                defects on the sample;            -   set a Field of View (FoV) of the electron-beam                inspection tool to a first size to locate a subset of                the defects;            -   determine a position of each defect of the subset of the                defects based on inspection data generated by the                electron-beam inspection tool during a scan of the                sample;            -   adjust the coordinates of the defects based on the                determined positions of the subset of the defects; and            -   set the FoV of the electron-beam inspection tool to a                second size to locate additional defects based on the                adjusted coordinates.    -   33. The controller of clause 32, wherein the electron-beam        inspection tool being configured to scan the sample with the        primary electron beam to generate the inspection data includes        the electron-beam inspection tool being configured to scan the        sample with a plurality of electron beams to generate the        inspection data.    -   34. The controller of any one of clauses 32 and 33, wherein the        first size is larger than the second size.    -   35. The controller of any one of clauses 32-34, wherein the        sample is an un-patterned wafer.    -   36. The controller of any one of clauses 32-35, wherein the        processor being configured to execute the instructions to cause        the controller to adjust the coordinates of the defects based on        the determined positions of the subset of the defects includes        the processor being further configured to execute the        instructions to cause the controller to:        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            subset of the defects;        -   map the coordinates acquired via the optical imaging tool to            a new set of coordinates, based on the transformation            relationship; and        -   set the new set of coordinates as the adjusted coordinates.    -   37. The controller of any one of clauses 32-35, wherein the        processor being configured to execute the instructions to cause        the controller to adjust the coordinates of the defects based on        the determined positions of the subset of the defects includes        the processor being further configured to execute the        instructions to cause the controller to:        -   select a number of defects;        -   control the electron-beam inspection tool to locate the            selected detects;        -   determine positions of the selected defects based on the            inspection data;        -   determine a transformation relationship for the coordinates            of the detects based on the determined positions of the            selected defects; and        -   adjust the coordinates of the defects based on the            transformation relationship.    -   38. The controller of clause 37, wherein the processor is        further configured to execute the instructions to cause the        controller to select at least two defects as the subset of the        defects.    -   39. The controller of clause 37, wherein the processor being        configured to execute the instructions to cause the controller        set the FoV of the electron-beam inspection tool to a second        size includes the processor being further configured to execute        the instructions to cause the controller to:        -   control the electron-beam inspection tool to locate a first            defect, the first defect being different from the selected            defects;        -   determine a position of the first defect based on the            inspection data;        -   determine a difference between the determined position of            the first defect and an adjusted coordinate of the first            defect; and        -   when the difference is equal to or below a predetermined            threshold, change the FoV of the electron-beam inspection            tool to the second size to locate additional defects based            on the adjusted coordinates.    -   40. The controller of clause 39, wherein the processor is        further configured to execute the instructions to cause the        controller to:        -   when the difference exceeds the predetermined threshold,            update the transformation relationship based on the            determined position of the first defect; and        -   further adjust the coordinates of the defects based on the            updated transformation relationship.    -   41. A computer-implemented method comprising:        -   acquiring, via an optical imaging tool, coordinates of            defects on a sample;        -   setting a Field of View (FoV) of an electron-beam inspection            tool to a first size to locate a subset of the defects;        -   determining a position of each defect of the subset of the            defects based on inspection data generated by the            electron-beam inspection tool during a scan of the sample;        -   adjusting the coordinates of the defects based on the            determined positions of the subset of the defects; and        -   setting the FoV of the electron-beam inspection tool to a            second size to locate additional defects based on the            adjusted coordinates.    -   42. The computer-implemented method of clause 41, wherein the        first size is larger than the second size.    -   43. The computer-implemented method of any one of clauses 41 and        42, wherein the sample is an un-patterned wafer.    -   44. The computer-implemented method of any one of clauses 41-43,        wherein setting a FoV of the electron-beam inspection tool to        the first size to locate the subset of the defects includes:        -   selecting a number of defects; and        -   controlling the electron-beam inspection tool to locate the            selected detects;    -   45. The computer-implemented method of clause 44, wherein        adjusting the coordinates of the defects based on the determined        positions of the subset of the defects includes:        -   determining a transformation relationship for the            coordinates of the detects based on the determined positions            of the selected defects;        -   mapping the coordinates of defects acquired via the optical            imaging tool to a new set of coordinates, based on the            transformation relationship; and        -   setting the new set of coordinates as the adjusted defects.    -   46. The computer-implemented method of clause 44, wherein the        number of the selected defects is two or more than two.    -   47. The computer-implemented method of clause 44, wherein        adjusting the coordinates of the defects based on the determined        positions of the subset of the defects further includes:        -   controlling the electron-beam inspection tool to locate a            first defect, the first defect being different from the            selected defects;        -   determining a position of the first defect based on the            inspection data;        -   determining a difference between the determined position of            the first defect and an adjusted coordinate of the first            defect; and        -   when the difference is equal to or below a predetermined            threshold, changing the FoV of the electron-beam inspection            tool to the second size and controlling the electron-beam            inspection tool to locate additional defects based on the            adjusted coordinates.    -   48. The computer-implemented method of clause 47, wherein        adjusting the coordinates of the defects based on the determined        positions of the subset of the defects further includes:        -   when the difference exceeds the predetermined threshold,            updating the transformation relationship based on the            determined position of the first defect; and        -   further adjusting the coordinates of the defects based on            the updated transformation relationship.    -   49. A non-transitory computer-readable medium storing a set of        instructions that are executable by a processor of a device to        cause the device to perform a method comprising:        -   acquiring, via an optical imaging tool, coordinates of            defects on a sample;        -   setting a Field of View (FoV) of an electron-beam inspection            tool to a first size to locate a subset of the defects;        -   determining a position of each defect of the subset of the            defects based on inspection data generated by the            electron-beam inspection tool during a scan of the sample;        -   adjusting the coordinates of the defects based on the            determined positions of the subset of the defects; and        -   setting the FoV of the electron-beam inspection tool to            locate additional defects based on the adjusted coordinates.    -   50. The non-transitory computer-readable medium of clause 49,        wherein the first size is larger than the second size.    -   51. The non-transitory computer-readable medium of any one of        clauses 49 and 50, wherein the sample is an un-patterned wafer.    -   52. The non-transitory computer-readable medium of any one of        clauses 49-51, wherein setting a FoV of the electron-beam        inspection tool to the first size and controlling the        electron-beam inspection tool to locate the subset of the        defects includes:        -   selecting a number of defects; and        -   controlling the electron-beam inspection tool to locate the            selected detects.    -   53. The non-transitory computer-readable medium of clause 52,        wherein adjusting the coordinates of the defects based on the        determined positions of the subset of the defects includes:        -   determining a transformation relationship for the            coordinates of the detects based on the determined positions            of the selected defects;        -   mapping the coordinates of defects acquired via the optical            imaging tool to a new set of coordinates, based on the            transformation relationship; and        -   setting the new set of coordinates as the adjusted            coordinates.    -   54. The non-transitory computer-readable medium of clause 52,        wherein the number of the selected defects is two or more than        two.    -   55. The non-transitory computer-readable medium of clause 52,        wherein adjusting the coordinates of the defects based on the        determined positions of the subset of the defects further        includes:        -   controlling the electron-beam inspection tool to locate a            first defect, the first defect being different from the            selected defects;        -   determining a position of the first defect based on the            inspection data;        -   determining a difference between the determined position of            the first defect and an adjusted coordinate of the first            defect; and        -   when the difference is equal to or below a predetermined            threshold, changing the FoV of the electron-beam inspection            tool to the second size to locate additional defects based            on the adjusted coordinates.    -   56. The non-transitory computer-readable medium of clause 55,        wherein adjusting the coordinates of the defects based on the        determined positions of the subset of the defects further        includes:        -   when the difference exceeds the predetermined threshold,            updating the transformation relationship based on the            determined position of the first defect; and            further adjusting the coordinates of the defects based on            the updated transformation relationship.    -   57. The defect review tool of clause 1, wherein the sample is a        bare wafer.    -   58. The defect review tool of clause 57, wherein the bare wafer        is an unpatterned wafer.

It will be appreciated that the present disclosure is not limited to theexact construction that has been described above and illustrated in theaccompanying drawings, and that various modifications and changes can bemade without departing from the scope thereof. It is intended that thescope of the invention should only be limited by the appended claims.

What is claimed is:
 1. A system comprising: an optical imaging toolincluding circuitry to illuminate a sample with light and detect lightscattered from the sample; an inspection tool including circuitry togenerate inspection data associated with the sample; and a controller incommunication with the optical imaging tool and the inspection tool, thecontroller including circuitry to: receive light-scattering datagenerated by the optical imaging tool; determine coordinates of defectson the sample based on the light-scattering data; set a Field of View(FoV) of the inspection tool to a first size to locate a subset of thedefects; determine a position of each defect of the subset of thedefects based on inspection data generated by the inspection tool basedon the sample; adjust the coordinates of the defects based on thedetermined positions of the subset of the defects; and set the FoV ofthe inspection tool to a second size to locate additional defects basedon the adjusted coordinates.
 2. The system of claim 1, wherein theinspection tool includes circuitry to scan the sample with multiplecharged-particle beams.
 3. The system of claim 1, further comprising: atransport device including circuitry and an actuator to transport thesample from the optical imaging tool to the inspection tool.
 4. Thesystem of claim 1, wherein the first size is larger than the secondsize.
 5. The system of claim 1, wherein the sample is an un-patternedwafer.
 6. The system of claim 1, wherein the controller includingcircuitry to adjust the coordinates of the defects based on thedetermined positions of the subset of the defects includes thecontroller including circuitry to: determine a transformationrelationship for the coordinates of the defects based on the determinedpositions of the subset of the defects; map the coordinates acquired viathe optical imaging tool to a new set of coordinates, based on thetransformation relationship; and set the new set of coordinates as theadjusted coordinates.
 7. The system of claim 1, wherein the controllerincluding circuitry to adjust the coordinates of the defects based onthe determined positions of the subset of the defects includes thecontroller including circuitry to: select a number of defects; controlthe inspection tool to locate the selected defects; determine positionsof the selected defects based on the inspection data; determine atransformation relationship for the coordinates of the defects based onthe determined positions of the selected defects; and adjust thecoordinates of the defects based on the transformation relationship. 8.The system of claim 7, wherein the controller has circuitry to select atleast two defects as the subset of the defects.
 9. The system of claim7, wherein the controller including circuitry to set the FoV of theinspection tool to a second size includes the controller includingcircuitry to: control the inspection tool to locate a first defect, thefirst defect being different from the selected defects; determine aposition of the first defect based on the inspection data; determine adifference between the determined position of the first defect and anadjusted coordinate of the first defect; and when the difference isequal to or below a predetermined threshold, change the FoV of theinspection tool to the second size to locate additional defects based onthe adjusted coordinates.
 10. The system of claim 9, wherein thecontroller includes circuitry to: when the difference exceeds thepredetermined threshold, update the transformation relationship based onthe determined position of the first defect; and further adjust thecoordinates of the defects based on the updated transformationrelationship.
 11. A controller coupled with an optical imaging tool andan inspection tool, the optical imaging tool being configured toilluminate a sample with light and detect light scattered from thesample, the inspection tool being configured to generate inspection dataassociated with the sample, the controller comprising: a memory storinginstructions; and a processor configured to execute the instructions tocause the controller to: acquire, via the optical imaging tool,coordinates of defects on the sample; set a Field of View (FoV) of theinspection tool to a first size to locate a subset of the defects;determine a position of each defect of the subset of the defects basedon the inspection data generated by the inspection tool during a scan ofthe sample; adjust the coordinates of the defects based on thedetermined positions of the subset of the defects; and set the FoV ofthe inspection tool to a second size to locate additional defects basedon the adjusted coordinates.
 12. The controller of claim 11, wherein theinspection tool being configured to generate the inspection dataincludes the inspection tool being configured to generate the inspectiondata with a plurality of electron beams.
 13. The controller of claim 11,wherein the first size is larger than the second size.
 14. Thecontroller of claim 11, wherein the sample is an un-patterned wafer. 15.The controller of claim 11, wherein the processor being configured toexecute the instructions to cause the controller to adjust thecoordinates of the defects based on the determined positions of thesubset of the defects includes the processor being further configured toexecute the instructions to cause the controller to: determine atransformation relationship for the coordinates of the defects based onthe determined positions of the subset of the defects; map thecoordinates acquired via the optical imaging tool to a new set ofcoordinates, based on the transformation relationship; and set the newset of coordinates as the adjusted coordinates.
 16. The controller ofclaim 11, wherein the processor being configured to execute theinstructions to cause the controller to adjust the coordinates of thedefects based on the determined positions of the subset of the defectsincludes the processor being further configured to execute theinstructions to cause the controller to: select a number of defects;control the inspection tool to locate the selected defects; determinepositions of the selected defects based on the inspection data;determine a transformation relationship for the coordinates of thedefects based on the determined positions of the selected defects; andadjust the coordinates of the defects based on the transformationrelationship.
 17. The controller of claim 16, wherein the processor isfurther configured to execute the instructions to cause the controllerto select at least two defects as the subset of the defects.
 18. Thecontroller of claim 16, wherein the processor being configured toexecute the instructions to cause the controller to set the FoV of theinspection tool to a second size includes the processor being furtherconfigured to execute the instructions to cause the controller to:control the inspection tool to locate a first defect, the first defectbeing different from the selected defects; determine a position of thefirst defect based on the inspection data; determine a differencebetween the determined position of the first defect and an adjustedcoordinate of the first defect; and when the difference is equal to orbelow a predetermined threshold, change the FoV of the electron-beaminspection tool to the second size to locate additional defects based onthe adjusted coordinates.
 19. The controller of claim 18, wherein theprocessor is further configured to execute the instructions to cause thecontroller to: when the difference exceeds the predetermined threshold,update the transformation relationship based on the determined positionof the first defect; and further adjust the coordinates of the defectsbased on the updated transformation relationship.
 20. Acomputer-implemented method comprising: acquiring, via an opticalimaging tool, coordinates of defects on a sample; setting a Field ofView (FoV) of an inspection tool to a first size to locate a subset ofthe defects; determining a position of each defect of the subset of thedefects based on inspection data generated by the inspection tool duringa scan of the sample; adjusting the coordinates of the defects based onthe determined positions of the subset of the defects; and setting theFoV of the inspection tool to a second size to locate additional defectsbased on the adjusted coordinates.